export {}

interface Point2D {
  x: number
  y: number
}
// interface Point3D {
//   x: number
//   y: number
//   z: number
// }
// 接口之间的继承
interface Point3D extends Point2D {
  z: number
}
let obj: Point3D = {
  x: 2,
  y: 7,
  z: 9,
}
